As the degree of compactness of terminals such as wireless terminals advances, it is desired for passive components such as filters etc. built-into terminal casing to also be miniaturized. In recent years, in particular, in filters utilizing electrical oscillators for LC's etc. used extensively in wireless communication, oscillator size depends on electrical length. This makes it difficult to make a filter small, and a new signal selection theory is therefore sought after.
Of these, micro electromechanical filters are being made using MEMS (Micro Electro Mechanical Systems) and NEMS (Nano Electro Mechanical Systems) technology are prospective candidates for providing next-generation filters.
This electrical filter utilizes mechanical oscillations and this configuration depends on the mass and a spring constant of an oscillating oscillator. It is therefore possible to reduce size by employing an electrical oscillator. For example, the size of an oscillator oscillating at 1 GHz depends on the shape and oscillating mode but is a magnitude of less than a few microns. Further, as the size of this kind of filter is less than a few microns, a method for manufacturing a micro oscillator and a method for detecting microscopic oscillations is necessary.
As shown, for example, in Japanese Patent Laid-open Publication No. Hei. 6-310976, there exist electromechanical filters employing micro oscillators of the related art where, for example, carbon nanotubes are employed as micro oscillators. Carbon nanotubes are tube-shaped substances that are extremely small in the order of nanometers where carbon atoms are linked together to form a lattice.
A mechanism for selecting signals for an electromechanical filter in Japanese Patent Laid-open Publication No. Hei. 6-310976 assumes a case where carbon nanotubes and fullerenes are made of dielectric material. Specifically, with electromechanical filters of the related art, two each of an electrode to which an input signal port is connected and an electrode to which an output signal port is connected are provided at respective ends of a carbon nanotube of a predetermined length. These electrodes then constitute an input terminal for applying a signal to a carbon nanotube and an output terminal.
With this electromechanical filter, a carbon nanotube oscillates at its own resonance frequency due to the piezoelectric effect as a result of a signal inputted at the input signal port, and an output to the output signal port due to the piezoelectric effect may then be taken as a voltage. Further, methods such as magnetomotive and laser Doppler interference techniques are also being examined as methods for detecting oscillation of micro oscillators of the related art.
However, currently, with regards to the carbon nanotubes and fullerenes shown in Patent Document 1, there are no reports of the piezoelectric effect being seen for ferroelectric insulators, but there are reports of the possession of extremely superior conductivity. There is therefore a problem with the technology of Patent Document 1 in that implementation is difficult due to assumptions concerning the physical properties of carbon nanotubes and fullerenes.
Further, at this electromechanical filter, in a method for detecting oscillation of an oscillator constituted by a microstructure where magnetomotive techniques are employed, an apparatus for generating a large external magnetic field is necessary, and this is therefore problematic with regards to microcoil manufacturing processes and ensuring space etc. In the case of detecting oscillation of an oscillator of the related art using laser Doppler interference techniques, it is difficult to have an oscillator constituting a target at a focal point, and moreover, it is difficult to obtain sufficient reflected light. Moreover, as a further oscillation detection method, a method is being investigated where a metal or silicon (Si) mirror for reflecting laser light is provided at the tip of a miniature to defect oscillation of the structure. However, in this method, detection of oscillation of a structure including a mirror takes place and detection of oscillation characteristics of the micro oscillator itself is difficult.